It is well known that catalysts based on mordenite are useful in isomerizing hydrocarbons. Catalysts based on mordenite which has been treated with an acid solution show especially good results when applied in those processes, as is described in e.g. U.S. Pat. No. 3,507,931. As zeolite beta is, like mordenite, a large-pore zeolite, it would be expected that zeolite beta when treated with an acid solution would give good results when applied in a hydroisomerization process. However, it was observed that a treatment with an acid solution did not improve the performance of zeolite beta, but even deteriorated it.
It has now been found that zeolite beta when treated with a solution having a pH of at least 9 does not only have higher activity and selectivity in hydroisomerization processes than untreated zeolite beta, but even shows better results than mordenite-based catalysts which are used commercially.